#include <bits/stdc++.h>
using namespace std;
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define int long long
signed main() {
  string S; cin >> S;
  map<char, int> cnt;
  REP(i,S.size()) cnt[S[i]]++;
  cout << min<int>({cnt['t'], cnt['r'], cnt['e']/2}) << endl;
}